Both stores appear to have a very strong business. So why doesn't either company create one in downtown Detroit where the demand would be a multiple of that in Lansing and East Lansing?
Living in downtown Vancouver, I would go to the grocery store every 1-2 days to get food, because it was close by so there was no reason to "stock up". However growing up in the suburbs, we would go to the grocery store once a week to get all the food for the entire week.
A large scale grocery store/costco style simply doesn't make much sense as the place you go shopping every 1-2 days. So its better to put it in the suburbs and have people from downtown go out of the city every few weeks to stock up on specific items.
There is no bad weather. There is only bad clothing!
But it is wild how easy it is to see Detroit's lack of grocery stores: https://www.google.com/maps/search/grocery+store/@42.4272993...
A family of four consumes more in a week than could realistically be hand-carried in a single trip by both parents.
Better to do shorter and more frequent visits on foot or bicycle. Combined with delivery services which are much more resource efficient than private cars for this purpose.
They have executed pretty well with one glaring exception. Nearly everyone needs a weekly supermarket visit. Until fairly recently the city had no supermarkets for a population of 650,000 people. Recently a Whole Foods opened downtown as well as a couple of supermarkets on eight mile on the edge of the city.
Those eight mile supermarkets were created to cash in on a multi-million dollar incentive offered by the state. However it was poorly worded, so while they're technically in the city the suburbs are right across the street.
Many affluent highly educated people live in downtown Detroit and are forced to own a car so they can travel to the edge of the city to buy groceries.
https://detroitgreenways.org/twenty-minute-neighborhoods/